Leah Hirsig was born [on 9 Apr 1883 - Ed.] in Switzerland into a large family in which she was one of nine children. At the age of two she moved with her mother and siblings to the United States, where she grew up in New York. On reaching adulthood she remained in the city, teaching at a public high school in the Bronx. She and her older sister Alma were drawn to the study of the occult, and this interest led them in the spring of 1918 to pay a visit to Aleister Crowley, who was living at the time in the Greenwich Village neighborhood of Manhattan. Crowley and Hirsig felt an immediate and instinctive connection. In January of 1919, he consecrated her as his Scarlet Woman. She adopted the magical name Alostrael, the womb (or grail) of God. Crowley also called her the Ape of Thoth, in reference to the companion of the god Tahuti who enables his ideas to become reality.
Hirsig indeed proved herself immediately able to assist Crowley in translating his ideas into reality. In 1920 they founded the Abbey of Thelema in the town of Cefalù on the coast of Sicily, thus realizing in concrete form the dream of the French literary genius and early Thelemite François Rabelais. At the Abbey, Hirsig was instrumental in guiding Crowley, the Prophet of the New Aeon, to a deeper understanding of the Law of Thelema. At a time of despair, Crowley wrote, What really pulled me from the pit was the courage, wisdom, understanding and divine enlightenment of the Ape herself. Over and over again, she smote into my soul that I must understand the way of the gods We must not look to the dead past, or gamble with the unformed future; we must live wholly in the present, wholly absorbed in the Great Work, 'unassuaged of purpose, delivered from the lust of result'. Only so could will be pure and perfect. Hirsig's role as Crowley's initiatrix reached a pinnacle in the spring of 1921 when she presided over his attainment of the grade of Ipsissimus, the only witness to the event.
In 1924 Crowley moved on to a new Scarlet Woman, Dorothy Olsen, but this did not lead Hirsig to abandon her commitment to Thelema. Her diary from this period reveals her continuing devotion to the Great Work, her renewal of her magical oaths, her ongoing invocations of Ra Hoor Khuit, and her consecration of herself as the bride of Chaos. In 1925, when Crowley asked her to serve again for a period as his scribe and secretary, she readily accepted; she was ready to give her assistance when it was necessary to the furtherance of his magical work and to the promulgation of the Law of Thelema. As Crowley wrote in his diary during the Cefalù period, She loves me for my work She knows and loves the God in me, not the man; and therefore she has conquered the great enemy that hides behind his clouds of poisonous gas, Illusion.
Hirsig ultimately returned to the United States and resumed her work as a schoolteacher. She died in [1975 in Meiringen, Switzerland - Ed.].

Sources:
Crowley, Aleister. The Confessions of Aleister Crowley.
Crowley, Aleister. The Magical Record of the Beast 666.
Hirsig, Leah. The Magical Record of the Scarlet Woman Alostrael 31-666-31.
Sutin, Lawrence. Do What Thou Wilt: A Life of Aleister Crowley.

[This essay has been supplemented with genealogical data found here:
http://pages.sbcglobal.net/jmaxit/hirsig/pafg06.htm]